Motor controller and electronic power steering apparatus

ABSTRACT

An angle calculator detects a rotation angle θa of a rotor. A three-phase/d-q axis converter outputs detected current id, iq on d-q coordinate axes by making a conversion, based on a corrected detection angle θc obtained by adding or subtracting an amount of detection deviation from a time point of current detection to or from the detection angle θa. A command current calculator calculates command current id*, iq* on the d-q coordinate axes based on a steering torque T and a speed S. A feedback controller calculates command voltages vd, vq on the d-q coordinate axes based on the command current id*, iq* and the detected current id, iq. A d-q axis/three-phase converter converts the command voltages vd, vq into three-phase command voltages, based on a corrected detection angle θb obtained by adding an amount of detection deviation from a time point when a motor is driven to the detection angle θa. The deviation can be eliminated by the command voltages, and the motor can be driven with high precision.

TECHNICAL FIELD

The present invention relates to a motor controller and an electronicpower steering apparatus equipped with the motor controller.

BACKGROUND ART

In the prior art, the electronic power steering apparatus for applyingthe steering assist force to the steering mechanism of the vehicle bydriving the electronic motor in response to the steering torque that thedriver applies to the steering wheel (handle) is employed. As theelectronic motor of the electronic power steering apparatus, the brushmotor is employed widely in the prior art. From the aspects of animprovement in reliability and durability, a reduction in inertia, etc.,the brushless motor is also employed nowadays.

In order to control a torque produced by the motor, commonly the motorcontroller detects an electric current flowing through the motor, andthen applies the PI control (proportional integral control) based on adifference between an electric current that is to be supplied to themotor and an electric current that is detected. This motor is thethree-phase brushless motor, for example. In order to detect theelectric current in two phases or more, two or three current sensors areprovided to the motor controller. Also, since a rotation angle of themotor is employed in the d-q axis/three-phase convention, variousoperations, etc., whose details are described later, the sensor such asthe resolver, the Hall IC, or the like is provided to sense the rotationangle of the motor.

In connection with the invention of this application, in JP-A-9-331693and JP-A-2006-56473, the configuration for estimating a rotation angleof the motor not to use the rotation angle sensor or the angularvelocity sensor for the motor is disclosed. Also, in JP-A-2007-118823and JP-A-2008-37399, the configuration for estimating a rotation angleof the motor when a failure is caused in the motor rotation angledetecting section is disclosed.

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

As described above, in the motor controller in the prior art, in manycases the motor rotation angle detecting section is provided. In thisevent, only when such motor rotation angle detecting section is notprovided (or only when such motor rotation angle detecting section isbroken down), the section for estimating the rotation angle of the motormay be provided.

However, an angle that is sensed by the motor rotation angle detectingsection varies every moment. Therefore, even though the motor rotationangle detecting section is provided, it is possible to say that thedetection angle does not always indicate a correct angle at the time ofcontrolling the motor. This is because a delay due to a calculatingtime, variation of detecting timing, variation of control timing, or thelike is caused. As a result, depending on the angle that is sensed bythe motor rotation angle detecting section, the motor control cannot bemade with good precision.

Therefore, it is an object of the present invention to provide a motorcontroller and an electronic power steering apparatus equipped with thesame, capable of applying a motor control with good precision based on adetected result of a rotation angle of a motor.

Means for Solving the Problems

A first invention provides a motor controller for driving a brushlessmotor, that includes an angle detecting section that detects a rotationangle of a rotor of the brushless motor; a drive controlling sectionthat calculates command values indicating levels of command voltages fordriving the brushless motor; and a motor driving section that drives thebrushless motor by using the voltages at the levels indicated by thecommand values calculated by the drive controlling section, wherein thedrive controlling section calculates the command value, based on acorrected detection angle obtained by adding or subtracting an amount ofdetection deviation, that corresponds to a time difference from a timepoint of angle detection by the angle detecting section, to or from anangle detected by the angle detecting section.

In a second invention according to the first invention, the drivecontrolling section includes a d-q axis/three-phase converting sectionthat converts the command voltages on d-q coordinate axes intothree-phase command voltages, based on a first corrected detection angleobtained by adding a first amount of detection deviation, thatcorresponds to a time difference between a time point of angle detectionby the angle detecting section and a time point when the brushless motoris driven by using the voltages at the levels indicated by the commandvalues, to the detection angle.

A third invention according to the second or the third invention,provides the motor controller further includes a current detectingsection that detects currents flowing through the brushless motor,wherein the drive controlling section includes a three-phase/d-q axisconverting section that converts three-phase current detected valuesdetected by the current detecting section into current detected valueson the d-q coordinate axes, based on a second corrected detection angleobtained by adding or subtracting a second amount of detectiondeviation, that corresponds to a time difference between a time point ofangle detection by the angle detecting section and a time point when thecurrents are detected by the current detecting section, to or from thedetection angle.

A fourth invention provides an electronic power steering apparatusequipped with the motor controller set forth in any one of the first tothird inventions.

ADVANTAGES OF THE INVENTION

According to the first invention, the command values are calculatedbased on the corrected detection angle that is obtained by adding orsubtracting an amount of detection deviation, that corresponds to a timedifference from a time point of angle detection by the angle detectingsection, to or from the detection angle. Therefore, the influence ofinconsistency in time such as a lag due to calculation times, adiscrepancy of the detection timing from other detection values exceptthe angle, a variation of control timing, or the like, for example, canbe eliminated, and the motor control can be applied with good precision.

According to the second invention, the conversion is made based on thefirst corrected detection angle that is obtained by adding a firstamount of detection deviation, that corresponds to a time differencebetween a time point of angle detection by the angle detecting sectionand a time point when the brushless motor is driven by using thevoltages at the level indicated by the command values, to the detectionangle. Therefore, the influence of the time difference (variation ofcontrol timing) can be eliminated, and the motor control can be appliedwith good precision.

According to the third invention, the conversion is made based on thesecond corrected detection angle that is obtained by adding orsubtracting a second amount of detection deviation, that corresponds toa time difference between a time point of angle detection by the angledetecting section and a time point when the currents are detected by thecurrent detecting section, to or from the detection angle. Therefore,the influence of the time difference (variation of control timing) canbe eliminated, and the motor control can be applied with good precision.

According to the fourth invention, the motor can be driven with highprecision. Therefore, a desired motor output can be obtained, and alsothe smooth steering assist can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A block diagram showing a configuration of an electronic powersteering apparatus according to an embodiment of the present invention.

FIG. 2 A block diagram showing a configuration of a motor controlleraccording to the above embodiment.

FIG. 3 A view showing three-phase AC coordinates and d-q coordinates ina three-phase brushless motor of the above embodiment.

FIG. 4 A view showing a relationship between a detection angle of arotor and a corrected detection angle in the three-phase brushless motorof the above embodiment.

DESCRIPTION OF REFERENCE NUMERALS

10 electronic control unit (ECU), 13 motor driving circuit, 20microcomputer.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be explained with referenceto the accompanying drawings hereinafter.

<1. Overall Configuration of an Electronic Power Steering Apparatus>

FIG. 1 is a schematic block diagram showing a configuration of anelectronic power steering apparatus according to an embodiment of thepresent invention, together with associated configurations of a vehicle.The electronic power steering apparatus shown in FIG. 1 is a columnassist type electronic power steering apparatus that is equipped with abrushless motor 1, a reduction gear 2, a torque sensor 3, a speed sensor4, a position sensor 5, and an electronic control unit (abbreviated as“ECU” hereinafter) 10.

As shown in FIG. 1, a steering wheel (handle) 101 is fixed to one end ofa steering shaft 102, and the other end of the steering shaft 102 iscoupled to a rack shaft 104 via a rack & pinion mechanism 103. Both endsof the rack shaft 104 are coupled to a wheel 106 via a coupling member105 consisting of a tie-rod and a knuckle arm respectively. When adriver turns the steering wheel 101, the steering shaft 102 is turnedand correspondingly the rack shaft 104 is moved reciprocally. Thedirection of the wheel 106 is changed according to a reciprocatingmotion of the rack shaft 104.

The electronic power steering apparatus executes the steering assistillustrated hereunder to reduce the load of the driver. The torquesensor 3 senses a steering torque T that is applied to the steeringshaft 102 by the operation of the steering wheel 101. The speed sensor 4senses a vehicle speed S. The position sensor 5 senses a rotationposition P of the rotor of the brushless motor 1. The position sensor 5is composed of the resolver, the Hall IC, or the like, for example.

The ECU 10 receives a supply of an electric power from an onboardbattery 100, and drives the brushless motor 1 based on the steeringtorque T, the vehicle speed S, and the rotation position P. Thebrushless motor 1 when driven by the ECU 10 produces a steering assistforce. The reduction gear 2 is provided between the brushless motor 1and the steering shaft 102. The steering assist force produced by thebrushless motor 1 is applied via the reduction gear 2 to turn thesteering shaft 102.

As a result, the steering shaft 102 is turned by both the steeringtorque applied to the steering wheel 101 and the steering assist forceproduced by the brushless motor 1. In this manner, the electronic powersteering apparatus performs the steering assist by applying the steeringassist force produced by the brushless motor 1 to the steering mechanismof the vehicle.

The electronic power steering apparatus according to the embodiments ofthe present invention is characterized by the control device (motorcontroller) that drives the brushless motor 1. Therefore, the motorcontroller contained in the electronic power steering apparatusaccording to the embodiments will be explained hereunder.

<2. Overall Configuration of a Motor Controller>

FIG. 2 is a block diagram showing a configuration of a motor controlleraccording to one embodiment of the present invention. The motorcontroller shown in FIG. 2 is constructed by using the ECU 10, anddrives the brushless motor 1 with three-phase windings (not shown) inu-phase, v-phase, and w-phase. The ECU 10 is equipped with a phasecompensator 11, a microcomputer 20, a three-phase/PWM (Pulse WidthModulation) modulator 12, a motor driving circuit 13, and a currentsensor 14.

The steering torque T output from the torque sensor 3, the vehicle speedS output from the speed sensor 4, and the rotation position P outputfrom the position sensor 5 are input into the ECU 10. The phasecompensator 11 applies a position compensation to the steering torque T.The microcomputer 20 functions as a controlling section for detecting avoltage command value used to drive the brushless motor 1. Details offunctions of the microcomputer 20 will be described later.

The three-phase/PWM modulator 12 and the motor driving circuit 13 areconstructed by hardware (circuit), and functions as a motor drivingsection for driving the brushless motor 1 by using a voltage at a leveldetected by the microcomputer 20. The three-phase/PWM modulator 12receives the voltage signal corresponding to the duty ratio from themicrocomputer 20 to produce three types of PWM signals (U, V, W shown inFIG. 2) that have a duty ratio to respond to the level of three-phasevoltage detected by the microcomputer 20, and produces three types ofPWM signals having such duty ratio. The motor driving circuit 13 is aPWM voltage type inverter circuit that contains six MOS-FETs (MetalOxide Semiconductor Field Effect Transistors) as the switching elements.Six MOS-FETs are controlled by three types of PWM signals and theirnegative signals. When the conduction states of the MOS-FETs arecontrolled by using the PWM signals, three-phase driving currents(U-phase current, V-phase current, and W-phase current) are supplied tothe brushless motor 1. In this manner, the motor driving circuit 13 hasa plurality of switching elements, and functions as a switching circuitthat supplies the currents to the brushless motor 1.

The current sensor 14 functions as a current detecting section fordetecting the current being flowing through the brushless motor 1. Thecurrent sensor 14 is composed of a resistor or a Hall element, forexample, and only one current sensor 14 is provided in respective phase,i.e., three current sensors 14 are provided in total, between the motordriving circuit 13 and a power supply. In an example shown in FIG. 2,the current sensor 14 is provided between the motor driving circuit 13and the minus side (GND) of the power supply. But the current sensor 14may be provided between the motor driving circuit 13 and the plus sideof the power supply. Three-phase detected current values iu, iv, iwsensed by the current sensors 14 are input into the microcomputer 20.

When a program stored in a memory (not shown) built in the ECU 10 isexecuted, the microcomputer 20 functions as a command current calculator21, a feedback controller 22, a d-q axis/three-phase converter 23, anangle calculator 24, and a three-phase/d-q axis converter 25. Asdiscussed hereinafter, the microcomputer 20 derives a level of thevoltage (referred to as a “command voltage” hereinafter) to be suppliedto the motor driving circuit 13 such that a deviation between a commandcurrent value indicating a quality of current to be supplied to thebrushless motor 1 and the detected current value of the brushless motor1 becomes zero. Functions of respective portions that are implementedwhen this microcomputer 20 operates will be explained in detailhereunder.

<3. Operation of a Microcomputer>

The angle calculator 24 as a functional element contained in themicrocomputer 20 calculates a rotation angle (referred to as an “angelθ” hereinafter) of the rotor of the brushless motor 1, based on therotation position P that the position sensor 5 detects. In this case, asshown in FIG. 3, when a u-axis, a v-axis, and a w-axis are set to thebrushless motor 1 and a d-axis and a q-axis are set to a rotor 6 of thebrushless motor 1, an angle between the u-axis and the d-axiscorresponds to the angel θ.

The three-phase/d-q axis converter 25 calculates a d-axis currentdetected value id and a q-axis current detected value iq on the d-qcoordinate axes by using following equations (1) and (2), based on thecurrent values iu, iv detected by the current sensors 14 on thethree-phase AC coordinate axes and the angel θ calculated by the anglecalculator 24.

id=√2×{iv×sin θc−iu×sin(θc−2π/3)}  (1)

iq=√2×{iv×cos θc−iu×cos(θc−2π/3)}  (2)

Here, an angle θc contained in above equations (1) and (2) is differentfrom the angel θ (represented as a detection angle θa hereinafter todiscriminate from other angles) calculated by the angle calculator 24.As shown in FIG. 4, this angle θc is given as the angle that goes backfrom the detection angle θa by a predetermined angle in the oppositedirection to the rotor rotating direction of the brushless motor 1,i.e., the angle that is earlier in time than the detection angle θa. Amethod of calculating this angle θc will be explained in detailhereinafter. In this event, an angle θb shown in FIG. 4 will bedescribed later.

First, a relationship between the equations (1) and (2) represents arelationship between the detected current value and the detection angleat the same point of time. However, because there is a limit to thenumber of A/D converters built in the microcomputer 20, themicrocomputer 20 may employ commonly one (or a set of plural) A/Dconverter in both uses of current detection and angle detection. In thiscase, the microcomputer 20 often acquires the current value that issubjected to the A/D conversion from the current sensors 14, and thenacquires the detection angle θa that is subjected to the A/D conversionfrom the angle calculator 24. Accordingly, in such case, a time point tcof angle detection in the angle calculator 24, which should coincidewith a time point of current detection in the current sensors 14,becomes earlier in time than an actual time point to of angle detection.

Therefore, in order to calculate the detection angle θc of the anglecalculator 24, which is located at an earlier time point by a timedifference T1 (=tc˜ta), from the detection angle θa at the present time,the angle θc can be expressed by a following equation (3) on theassumption that a rotation angular velocity ω of the brushless motor 1is kept substantially constant from the time point tc to the time pointta.

θc=θa−T1×ω  (3)

Also, the similar consideration can be applied even when the currentdetection and the angle detection are executed in the opposite order tothe above, i.e., the microcomputer 20 acquires the detection angle θathat is subjected to the A/D conversion from the angle calculator 24,and then acquires the current value that is subjected to the A/Dconversion from the current sensors 14. In this case, unlike the caseshown in FIG. 4, a time point tc′ of angle detection in the anglecalculator 24, which should coincide with a time point of currentdetection in the current sensors 14, becomes later in time than anactual time point ta of angle detection. Therefore, in order tocalculate the detection angle θc of the angle calculator 24, which islocated at a later time point by a time difference T1 (=ta˜tc′), fromthe detection angle θa at the present time, the angle θc can beexpressed by a following equation (3)′ on the assumption that a rotationangular velocity ω of the brushless motor 1 is kept substantiallyconstant from the time point ta to the time point tc′.

θc=θa+T1×ω  (3)′

Here, the angular velocity ω can be obtained by differentiating thedetection angle in the angle calculator 24. Also, for example, adifference between a stored value of the detection angle being storedearlier by a predetermined time and the detection angle may becalculated, and then a predetermined value corresponding to thecalculated value may be employed as a value corresponding to the angularvelocity ω.

As described above, the three-phase/d-q axis converter 25 adds orsubtracts an amount of detection deviation T1×ω, which corresponds to atime difference between a time point of angle detection and a time pointof current detection in the current sensors 14, to or from the detectionangle θa calculated by the angle calculator 24, and then converts thecurrent values iu, iv, iw detected by the current sensors 14 on thethree-phase AC coordinate axes into the d-axis detected current id andthe q-axis detected current iq on the d-q coordinate axes, based on theresultant corrected detection angle θc. The converted d-axis detectedcurrent id and the converted q-axis detected current iq are fed to thefeedback controller 22.

The command current calculator 21 calculates a d-axis current and aq-axis current to be supplied to the brushless motor 1 (the former isreferred to as a “d-axis command current id*” hereinafter, and thelatter is referred to as a “q-axis command current iq*” hereinafter),based on the steering torque T after the phase compensation (outputsignal of the phase compensator 11) and the velocity speed S. In moredetail, the command current calculator 21 has a built-in table in whichcorrespondences between the steering torque T and the command currentare stored using the vehicle speed S as a parameter (referred to as an“assist map” hereinafter), and calculates the command current byreferring to an assist map. When the steering torque is given at somemagnitude, the d-axis command current id* and the q-axis command currentiq*, which are supplied to the brushless motor 1 to produce the steeringassist force having an adequate magnitude in response to a magnitude ofthe steering torque, can be detected by using the assist map. Thedetected d-axis command current id* and the detected q-axis commandcurrent iq* are fed to the feedback controller 22.

In this case, the q-axis command current iq* calculated by the commandcurrent calculator 21 is a current value with sign, and the signindicates the direction of the steering assist. For example, thesteering assist is applied to turn rightward when the sign is plus, andthe steering assist is applied to turn leftward when the sign is minus.Also, typically the d-axis command current id* is set to zero.

The feedback controller 22 applies the well-known proportional integraloperation to the current variations such that the current variationbetween the d-axis command current id* and the d-axis detected currentid and the current variation between the q-axis command current iq* andthe q-axis detected current iq become zero respectively, and thuscalculates a d-axis voltage and a q-axis voltage, which are supplied tothe brushless motor 1 (the former is referred to as a “d-axis commandvoltage vd” hereinafter, and the latter is referred to as a “q-axiscommand voltage vq” hereinafter).

In fact, commonly the d-axis detected current id is often controlled tozero because this current does not contribute to a generation of themotor torque. However, when the so-called flux-weakening control(field-weakening control) is applied, the d-axis detected current id iscontrolled to flow.

The d-q axis/three-phase converter 23 converts the d-axis commandvoltage vd and the q-axis command voltage vq calculated by the feedbackcontroller 22 into the command voltages on the three-phase AC coordinateaxis. In more detail, the d-q axis/three-phase converter 23 calculates au-phase command voltage Vu, a v-phase command voltage Vv, and a w-phasecommand voltage Vw by using following equations (4) to (6), based on thed-axis command voltage vd and the q-axis command voltage vq.

Vu=√/(2/3)×{vd×cos θb−vq×sin θb}  (4)

Vv=√(2/3)×{vd×cos(θb−2π/3)−vq×sin(θb−2π/3)}  (5)

Vw=−Vu−Vv  (6)

Here, an angle Ob contained in above equations (4) and (5) is differentfrom the detected angel θa calculated by the angle calculator 24. Asshown in FIG. 4, this angle θb is given as the angle that goes to thedetection angle θa by a predetermined angle in the rotor rotatingdirection of the brushless motor 1, i.e., the angle that is later intime than the detection angle θa. A method of calculating this angle θbwill be explained in detail hereinafter.

First, a relationship between the equations (4) and (5) represents arelationship between the command voltage and the detection angle at thesame point of time. In this case, the command voltage indicates a dutyratio of the PWM signal that is to be output from the three-phase/PWMmodulator 12. Hence, it is possible to say that the point of time whenthe electric current responding to this PWM signal flows through thethree-phase windings of the brushless motor 1 and the rotor of thebrushless motor 1 is rotated corresponds to the point of time when thecontrol should be applied by using the command voltages. Accordingly, atime point tb of angle detection in the angle calculator 24, whichshould coincide with a time point when the control should be applied byusing the command voltages, becomes later in time than an actual timepoint ta of angle detection.

Therefore, in order to calculate the detection angle θb of the anglecalculator 24, which is located at a later time point by a timedifference T2 (=ta˜tb), from the detection angle θa at the present time,the angle θb can be expressed by a following equation (7) on theassumption that the rotation angular velocity ω of the brushless motor 1is kept substantially constant from the time point ta to the time pointtb.

θb=θa+T2×ω  (7)

Here, it is described above that the angular velocity ω can be obtainedby differentiating the detection angle in the angle calculator 24.

Concretely, the time point that is subsequent to the time point when thevoltage is applied to the brushless motor 1 from the motor drivingcircuit 13, e.g., a time point when the next current value is acquiredfrom the current sensor 14 or a time point that is just before the timepoint when the next current value is acquired, or the like, ispreferable as the time point when the control should be applied by usingthe command voltages (i.e., the time point tb of angle detection).

As described above, the d-q axis/three-phase converter 23 adds an amountof detection deviation T2×ω, which corresponds to a time differencebetween a time point of angle detection by the angle calculator 24 and atime point when the brushless motor 1 is driven by using the voltage atthe level indicated by the command value, to the detection angle θacalculated by the angle calculator 24, and converts the d-axis commandvoltage vd and the q-axis command voltage vq into the u-phase commandvoltage Vu, the v-phase command voltage Vv, and the w-phase commandvoltage Vw based on the corrected detection angle θb that is obtained asthe added result. The converted u-phase command voltage Vu, theconverted v-phase command voltage Vv, and the converted w-phase commandvoltage Vw are output to the three-phase/PWM modulator 12 as the voltagesignal that indicates a duty ratio of the PWM signal to be output fromthe three-phase/PWM modulator 12, based on the power supply voltage thatis detected by the power supply (here, the battery) voltage detector(not shown).

In this manner, the microcomputer 20 functions as a motor drivecontrolling section that executes a process of calculating the commandcurrents id*, iq* on the d-q coordinate axes, a process of convertingthe three-phase detected current values iu, iv, iw into the detectedcurrents id, iq on the d-q coordinate axes, a process of calculating thecommand voltages vd, vq on the d-q coordinate axes, and a process ofconverting the command voltages vd, vq on the d-q coordinate axes intothe three-phase command voltages Vu, Vv, Vw.

The three-phase/PWM modulator 12 outputs three types of PWM signalsbased on the voltage signal indicating a duty ratio in response to thethree-phase command voltages Vu, Vv, Vw given by the microcomputer 20.Accordingly, the sine-wave currents responding to the command voltagesin respective phases flow through the three-phase windings of thebrushless motor 1, and the rotor of the brushless motor 1 is rotated. Atorque that responds to the currents that flow through the brushlessmotor 1 is generated by the rotation shaft of the brushless motor 1. Thegenerated torque is employed in the steering assist.

<4. Advantages>

As described above, in the motor controller according to the presentembodiment, the three-phase/d-q axis converter 25 executes theconversion based on the corrected detection angle θc that is obtained byadding or subtracting an amount of detection deviation, whichcorresponds to a time difference from a time point of current detection,to or from the detection angle θa calculated by the angle calculator 24,and also the d-q axis/three-phase converter 23 executes the conversionbased on the corrected detection angle θb that is obtained by adding anamount of detection deviation, which corresponds to a time differencefrom a time point when the brushless motor 1 is driven, to the detectionangle θa.

As a result, according to the motor controller according to the presentembodiment, the influence of inconsistency in time such as a lag due tocalculation times, a discrepancy of the detection timing from otherdetection values except the angle, a variation of control timing, or thelike can be eliminated by correcting the angle detected by the motorrotation angle detecting section, and the motor control can be appliedwith good precision.

Also, according to the electronic power steering apparatus equipped withthis motor controller, the motor can be driven with high precision.Therefore, a desired motor output can be obtained, and also the smoothsteering assist can be provided.

<5. Variation>

In the present embodiment, the configuration in which the feedbackcontrol is applied by the feedback controller 22 is employed, but theconfiguration in which the well-known open-loop control is applied maybe employed instead of the above configuration. In this open-loopcontrol, the d-axis command voltage vd and the q-axis command voltage vqare calculated by using following equations (8) and (9).

vd=(R+PLd)id*−ωeLqie*  (8)

vq(R+PLq)iq*+ωeLdid*+ωe Φ  (9)

Where, in the equations (8) and (9), ωe is the angular velocity of therotor, R is the circuit resistance containing the armature windingresistance, Ld is the d-axis self-inductance, Lq is the q-axisself-inductance, Φ is the √(2/3) multiple of the maximum value of thearmature winding flux linkage number in U, V, W phases, and P is thedifferential operator P. Out of them, R, Ld, Lq, and Φ are handled asthe already-known parameters.

In this manner, when the open-loop control is applied, the angularvelocity of the rotor is required for the control. Therefore, when thisangular velocity is derived by differentiating the detection angle θacalculated by the angle calculator 24, the angular velocity may becalculated based on the corrected detection angle θc that is obtained bycorrecting the detection angle θa by the angle calculator 24, like thecase in the three-phase/d-q axis converter 25. In this case, theabove-mentioned corrected detection angle may be calculated by takingfurther a time required for the differentiating operation into aconsideration. Also, even when a sensor for detecting directly theangular velocity, or the like is provided, the similar consideration tothe above can be applied.

Also, when the flux-weakening control (field-weakening control) isapplied even in not only a situation that the open-loop control isapplied but also a situation that the feedback control in the presentembodiment is applied, the d-axis command voltage vd is calculated byusing above equation (8), and thus the angular velocity is similarlyemployed. Accordingly, in this case, the angular velocity may also becalculated based on the corrected detection angle θc that is obtained bycorrecting the detection angle θa by the angle calculator 24, like thecase in the three-phase/d-q axis converter 25.

Further, when various operations are executed for the purpose ofwell-known controls using the detection angle θa (or the angularvelocity as its derivative or the angular acceleration as its secondderivative) calculated by the angle calculator 24, the angular velocitymay be calculated, based on the corrected detection angle θc that isobtained by correcting the detection angle θa by the angle calculator24, like the case in the three-phase/d-q axis converter 25 or the d-qaxis/three-phase converter 23 (or while further considering thecalculation time, or the like into a consideration).

1-4. (canceled)
 5. A motor controller for driving a brushless motor,comprising: an angle detecting section that detects a rotation angle ofa rotor of the brushless motor; a drive controlling section thatcalculates command values indicating levels of command voltages fordriving the brushless motor; a motor driving section that drives thebrushless motor by using the voltages at the levels indicated by thecommand values calculated by the drive controlling section; and acurrent detecting section that detects currents flowing through thebrushless motor, wherein the drive controlling section calculates thecommand value, based on a corrected detection angle obtained by addingor subtracting an amount of detection deviation, that corresponds to atime difference from a time point of angle detection by the angledetecting section, to or from an angle detected by the angle detectingsection; wherein the drive controlling section includes a d-qaxis/three-phase converting section that converts the command voltageson d-q coordinate axes into three-phase command voltages, based on afirst corrected detection angle obtained by adding a first amount ofdetection deviation, that corresponds to a time difference between atime point of angle detection by the angle detecting section and a timepoint when the brushless motor is driven by using the voltages at thelevels indicated by the command values, to the detection angles; andwherein the time point of the angle detection by the angle detectingsection is subsequent to a time point when the voltages are applied tothe brushless motor by the motor driving section, and is a time pointwhen next current values are acquired from the current detecting sectionor a time point just before the time.
 6. The motor controller accordingto claim 5, wherein the drive controlling section includes athree-phase/d-q axis converting section that converts three-phasecurrent detected values detected by the current detecting section intocurrent detected values on the d-q coordinate axes, based on a secondcorrected detection angle obtained by adding or subtracting a secondamount of detection deviation, that corresponds to a time differencebetween a time point of angle detection by the angle detecting sectionand a time point when the currents are detected by the current detectingsection, to or from the detection angle.
 7. The motor controlleraccording to claim 5, wherein the drive controlling section performs anopen-loop control.
 8. An electronic power steering apparatus including amotor controller for driving a brushless motor, wherein the motorcontroller includes: an angle detecting section that detects a rotationangle of a rotor of the brushless motor; a drive controlling sectionthat calculates command values indicating levels of command voltages fordriving the brushless motor; a motor driving section that drives thebrushless motor by using the voltages at the levels indicated by thecommand values calculated by the drive controlling section; and acurrent detecting section that detects currents flowing through thebrushless motor; wherein the drive controlling section calculates thecommand value, based on a corrected detection angle obtained by addingor subtracting an amount of detection deviation, that corresponds to atime difference from a time point of angle detection by the angledetecting section, to or from an angle detected by the angle detectingsection; wherein the drive controlling section includes a d-qaxis/three-phase converting section that converts the command voltageson d-q coordinate axes into three-phase command voltages, based on afirst corrected detection angle obtained by adding a first amount ofdetection deviation, that corresponds to a time difference between atime point of angle detection by the angle detecting section and a timepoint when the brushless motor is driven by using the voltages at thelevels indicated by the command values, to the detection angle; andwherein the time point of the angle detection by the angle detectingsection is subsequent to a time point when the voltages are applied tothe brushless motor by the motor driving section, and is a time pointwhen next current values are acquired from the current detecting sectionor a time point just before the time.
 9. The electronic power steeringapparatus according to claim 8, wherein the drive controlling sectionincludes a three-phase/d-q axis converting section that convertsthree-phase current detected values detected by the current detectingsection into current detected values on the d-q coordinate axes, basedon a second corrected detection angle obtained by adding or subtractinga second amount of detection deviation, that corresponds to a timedifference between a time point of angle detection by the angledetecting section and a time point when the currents are detected by thecurrent detecting section, to or from the detection angle.
 10. Theelectronic power steering apparatus according to claim 8, wherein thedrive controlling section performs an open-loop control.